INFO: task syz-executor.0:10594 blocked for more than 143 seconds. Not tainted 5.14.0-rc3-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.0 state:D stack:27728 pid:10594 ppid: 8456 flags:0x00000004 Call Trace: context_switch kernel/sched/core.c:4683 [inline] __schedule+0x93a/0x26f0 kernel/sched/core.c:5940 schedule+0xd3/0x270 kernel/sched/core.c:6019 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6078 __mutex_lock_common kernel/locking/mutex.c:1036 [inline] __mutex_lock+0x7b6/0x10a0 kernel/locking/mutex.c:1104 device_lock include/linux/device.h:754 [inline] usbdev_release+0x83/0x4b0 drivers/usb/core/devio.c:1074 __fput+0x288/0x920 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:175 [inline] exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:209 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline] syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4193fb RSP: 002b:00007ffe6085eb80 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000006 RCX: 00000000004193fb RDX: 0000001b2c231b8c RSI: 00007f92b22d8000 RDI: 0000000000000005 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000001b2c22e520 R10: 0000000000001f50 R11: 0000000000000293 R12: 000000000056cb00 R13: 000000000056cb00 R14: 000000000056bf80 R15: 0000000000039722 INFO: task syz-executor.1:10596 blocked for more than 143 seconds. Not tainted 5.14.0-rc3-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.1 state:D stack:27088 pid:10596 ppid: 8457 flags:0x00000004 Call Trace: context_switch kernel/sched/core.c:4683 [inline] __schedule+0x93a/0x26f0 kernel/sched/core.c:5940 schedule+0xd3/0x270 kernel/sched/core.c:6019 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6078 __mutex_lock_common kernel/locking/mutex.c:1036 [inline] __mutex_lock+0x7b6/0x10a0 kernel/locking/mutex.c:1104 device_lock include/linux/device.h:754 [inline] usbdev_release+0x83/0x4b0 drivers/usb/core/devio.c:1074 __fput+0x288/0x920 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:175 [inline] exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:209 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline] syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4193fb RSP: 002b:00007ffeb17dc2d0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000006 RCX: 00000000004193fb RDX: 0000001b2c328e14 RSI: ffffffff8155e737 RDI: 0000000000000005 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000001b2c3277dc R10: 000000000000030a R11: 0000000000000293 R12: 000000000056cb00 R13: 000000000056cb00 R14: 000000000056bf80 R15: 0000000000039731 INFO: task syz-executor.2:10595 blocked for more than 143 seconds. Not tainted 5.14.0-rc3-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.2 state:D stack:27160 pid:10595 ppid: 8459 flags:0x00000004 Call Trace: context_switch kernel/sched/core.c:4683 [inline] __schedule+0x93a/0x26f0 kernel/sched/core.c:5940 schedule+0xd3/0x270 kernel/sched/core.c:6019 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6078 __mutex_lock_common kernel/locking/mutex.c:1036 [inline] __mutex_lock+0x7b6/0x10a0 kernel/locking/mutex.c:1104 device_lock include/linux/device.h:754 [inline] usbdev_release+0x83/0x4b0 drivers/usb/core/devio.c:1074 __fput+0x288/0x920 fs/file_table.c:280 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:175 [inline] exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:209 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline] syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4193fb RSP: 002b:00007ffd25293950 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000006 RCX: 00000000004193fb RDX: 0000001b2c634d64 RSI: 00007fcf6e766000 RDI: 0000000000000005 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000001b2c62e65c R10: 0000000000001f92 R11: 0000000000000293 R12: 000000000056cb00 R13: 000000000056cb00 R14: 000000000056bf80 R15: 0000000000039c65 INFO: task syz-executor.3:10636 blocked for more than 143 seconds. Not tainted 5.14.0-rc3-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.3 state:D stack:27656 pid:10636 ppid: 8461 flags:0x00004004 Call Trace: context_switch kernel/sched/core.c:4683 [inline] __schedule+0x93a/0x26f0 kernel/sched/core.c:5940 schedule+0xd3/0x270 kernel/sched/core.c:6019 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6078 __mutex_lock_common kernel/locking/mutex.c:1036 [inline] __mutex_lock+0x7b6/0x10a0 kernel/locking/mutex.c:1104 device_lock include/linux/device.h:754 [inline] usbdev_open+0x19d/0x930 drivers/usb/core/devio.c:1029 chrdev_open+0x266/0x770 fs/char_dev.c:414 do_dentry_open+0x4c8/0x11d0 fs/open.c:826 do_open fs/namei.c:3374 [inline] path_openat+0x1c23/0x27f0 fs/namei.c:3507 do_filp_open+0x1aa/0x400 fs/namei.c:3534 do_sys_openat2+0x16d/0x420 fs/open.c:1204 do_sys_open fs/open.c:1220 [inline] __do_sys_openat fs/open.c:1236 [inline] __se_sys_openat fs/open.c:1231 [inline] __x64_sys_openat+0x13f/0x1f0 fs/open.c:1231 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4196d4 RSP: 002b:00007f0b7cf64cc0 EFLAGS: 00000293 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 6666666666666667 RCX: 00000000004196d4 RDX: 0000000000000001 RSI: 00007f0b7cf64d60 RDI: 00000000ffffff9c RBP: 00007f0b7cf64d60 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001 R13: 00007ffc210355cf R14: 00007f0b7cf65300 R15: 0000000000022000 INFO: task syz-executor.5:10637 blocked for more than 144 seconds. Not tainted 5.14.0-rc3-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.5 state:D stack:28488 pid:10637 ppid: 8465 flags:0x00000004 Call Trace: context_switch kernel/sched/core.c:4683 [inline] __schedule+0x93a/0x26f0 kernel/sched/core.c:5940 schedule+0xd3/0x270 kernel/sched/core.c:6019 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6078 __mutex_lock_common kernel/locking/mutex.c:1036 [inline] __mutex_lock+0x7b6/0x10a0 kernel/locking/mutex.c:1104 device_lock include/linux/device.h:754 [inline] usbdev_open+0x19d/0x930 drivers/usb/core/devio.c:1029 chrdev_open+0x266/0x770 fs/char_dev.c:414 do_dentry_open+0x4c8/0x11d0 fs/open.c:826 do_open fs/namei.c:3374 [inline] path_openat+0x1c23/0x27f0 fs/namei.c:3507 do_filp_open+0x1aa/0x400 fs/namei.c:3534 do_sys_openat2+0x16d/0x420 fs/open.c:1204 do_sys_open fs/open.c:1220 [inline] __do_sys_openat fs/open.c:1236 [inline] __se_sys_openat fs/open.c:1231 [inline] __x64_sys_openat+0x13f/0x1f0 fs/open.c:1231 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4196d4 RSP: 002b:00007fb49e1cdcc0 EFLAGS: 00000293 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 6666666666666667 RCX: 00000000004196d4 RDX: 0000000000000001 RSI: 00007fb49e1cdd60 RDI: 00000000ffffff9c RBP: 00007fb49e1cdd60 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001 R13: 00007fff1649d7bf R14: 00007fb49e1ce300 R15: 0000000000022000 INFO: task syz-executor.4:10651 blocked for more than 144 seconds. Not tainted 5.14.0-rc3-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.4 state:D stack:27128 pid:10651 ppid: 8463 flags:0x00004004 Call Trace: context_switch kernel/sched/core.c:4683 [inline] __schedule+0x93a/0x26f0 kernel/sched/core.c:5940 schedule+0xd3/0x270 kernel/sched/core.c:6019 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6078 __mutex_lock_common kernel/locking/mutex.c:1036 [inline] __mutex_lock+0x7b6/0x10a0 kernel/locking/mutex.c:1104 device_lock include/linux/device.h:754 [inline] usbdev_open+0x19d/0x930 drivers/usb/core/devio.c:1029 chrdev_open+0x266/0x770 fs/char_dev.c:414 do_dentry_open+0x4c8/0x11d0 fs/open.c:826 do_open fs/namei.c:3374 [inline] path_openat+0x1c23/0x27f0 fs/namei.c:3507 do_filp_open+0x1aa/0x400 fs/namei.c:3534 do_sys_openat2+0x16d/0x420 fs/open.c:1204 do_sys_open fs/open.c:1220 [inline] __do_sys_openat fs/open.c:1236 [inline] __se_sys_openat fs/open.c:1231 [inline] __x64_sys_openat+0x13f/0x1f0 fs/open.c:1231 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4196d4 RSP: 002b:00007f640aab1cc0 EFLAGS: 00000293 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 6666666666666667 RCX: 00000000004196d4 RDX: 0000000000000001 RSI: 00007f640aab1d60 RDI: 00000000ffffff9c RBP: 00007f640aab1d60 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001 R13: 00007fffbd511c8f R14: 00007f640aab2300 R15: 0000000000022000 Showing all locks held in the system: 5 locks held by kworker/1:0/20: #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:620 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:617 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x871/0x1630 kernel/workqueue.c:2247 #1: ffffc90000da7db0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x8a5/0x1630 kernel/workqueue.c:2251 #2: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:754 [inline] #2: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: hub_event+0x1c1/0x4330 drivers/usb/core/hub.c:5662 #3: ffff8880187a0578 (&port_dev->status_lock){+.+.}-{3:3}, at: usb_lock_port drivers/usb/core/hub.c:3086 [inline] #3: ffff8880187a0578 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect drivers/usb/core/hub.c:5279 [inline] #3: ffff8880187a0578 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect_change drivers/usb/core/hub.c:5488 [inline] #3: ffff8880187a0578 (&port_dev->status_lock){+.+.}-{3:3}, at: port_event drivers/usb/core/hub.c:5634 [inline] #3: ffff8880187a0578 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_event+0x2178/0x4330 drivers/usb/core/hub.c:5716 #4: ffff888016de7c68 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_port_init+0x1b5/0x2f10 drivers/usb/core/hub.c:4703 5 locks held by kworker/1:1/25: #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:620 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:617 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x871/0x1630 kernel/workqueue.c:2247 #1: ffffc90000dffdb0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x8a5/0x1630 kernel/workqueue.c:2251 #2: ffff8880214d9220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:754 [inline] #2: ffff8880214d9220 (&dev->mutex){....}-{3:3}, at: hub_event+0x1c1/0x4330 drivers/usb/core/hub.c:5662 #3: ffff8880214dc578 (&port_dev->status_lock){+.+.}-{3:3}, at: usb_lock_port drivers/usb/core/hub.c:3086 [inline] #3: ffff8880214dc578 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect drivers/usb/core/hub.c:5279 [inline] #3: ffff8880214dc578 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect_change drivers/usb/core/hub.c:5488 [inline] #3: ffff8880214dc578 (&port_dev->status_lock){+.+.}-{3:3}, at: port_event drivers/usb/core/hub.c:5634 [inline] #3: ffff8880214dc578 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_event+0x2178/0x4330 drivers/usb/core/hub.c:5716 #4: ffff888015ccdf68 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_port_init+0x1b5/0x2f10 drivers/usb/core/hub.c:4703 1 lock held by khungtaskd/1633: #0: ffffffff8b97ba40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6446 5 locks held by kworker/1:6/9757: #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:620 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:617 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: ffff888018a39538 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x871/0x1630 kernel/workqueue.c:2247 #1: ffffc90016a1fdb0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x8a5/0x1630 kernel/workqueue.c:2251 #2: ffff888146d4d220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:754 [inline] #2: ffff888146d4d220 (&dev->mutex){....}-{3:3}, at: hub_event+0x1c1/0x4330 drivers/usb/core/hub.c:5662 #3: ffff888146d68578 (&port_dev->status_lock){+.+.}-{3:3}, at: usb_lock_port drivers/usb/core/hub.c:3086 [inline] #3: ffff888146d68578 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect drivers/usb/core/hub.c:5279 [inline] #3: ffff888146d68578 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect_change drivers/usb/core/hub.c:5488 [inline] #3: ffff888146d68578 (&port_dev->status_lock){+.+.}-{3:3}, at: port_event drivers/usb/core/hub.c:5634 [inline] #3: ffff888146d68578 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_event+0x2178/0x4330 drivers/usb/core/hub.c:5716 #4: ffff888146d1c168 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_port_init+0x1b5/0x2f10 drivers/usb/core/hub.c:4703 1 lock held by syz-executor.0/10594: #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:754 [inline] #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: usbdev_release+0x83/0x4b0 drivers/usb/core/devio.c:1074 1 lock held by syz-executor.1/10596: #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:754 [inline] #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: usbdev_release+0x83/0x4b0 drivers/usb/core/devio.c:1074 1 lock held by syz-executor.2/10595: #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:754 [inline] #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: usbdev_release+0x83/0x4b0 drivers/usb/core/devio.c:1074 1 lock held by syz-executor.3/10636: #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:754 [inline] #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: usbdev_open+0x19d/0x930 drivers/usb/core/devio.c:1029 1 lock held by syz-executor.5/10637: #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:754 [inline] #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: usbdev_open+0x19d/0x930 drivers/usb/core/devio.c:1029 1 lock held by syz-executor.4/10651: #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:754 [inline] #0: ffff88802139c220 (&dev->mutex){....}-{3:3}, at: usbdev_open+0x19d/0x930 drivers/usb/core/devio.c:1029 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1633 Comm: khungtaskd Not tainted 5.14.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105 nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105 nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline] watchdog+0xd0a/0xfc0 kernel/hung_task.c:295 kthread+0x3e5/0x4d0 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline] NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline] NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline] NMI backtrace for cpu 1 skipped: idling at acpi_idle_do_entry+0x1c6/0x250 drivers/acpi/processor_idle.c:553